I've had that happen, on everything since iOS 7.x. More so on iOS 8, and 9. This is between the 4s, 5, 5c, and 6 Plus that I've had. Most often on the 6 Plus. Just a blank screen. Haven't had it happen recently but I've seen it if that makes you feel any better.

Usually I'll just kill it in the task switcher and it's fine, or reboot.

Well even going by issues in iOS 8 and 7 already doesn't make it something new as it relates to iOS 9. But going even further back, there have certainly been plenty of threads about people dealing with all kinds of bypass scenarios (which are quite critical), to crashes of different kids, to things not working as they should, etc. I don't have much time to dig through to look for particular threads with particular examples being on a limited mobile connection for the moment, but I'll see if I can take a look when I'm on anode solid connection for longer. That said, I'm sure plenty of iOS "veterans" would recall similar things about previous iOS versions as I recall them in various other threads where this kind of discussion came up.

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